For light emitting elements used in e.g. illumination devices, display devices, and traffic signals, there is an increasing demand for higher brightness.
A metal reflection layer can be provided below the light emitting layer. Then, the emission light directed downward from the light emitting layer is reflected. This increases the upward light extraction efficiency and facilitates increasing the brightness. In this case, for instance, a silicon (Si) substrate can be wafer bonded to a semiconductor substrate including the light emitting layer. Then, the crystal growth substrate can be removed to form a thin film multilayer light emitting element. This facilitates increasing the volume productivity.
The reflectance of a metal film decreases as the wavelength of visible light becomes shorter. In particular, the light reflectance of a stable electrode metal such as Au, Pt, and Pd decreases to 60% or less at 450 nm. This makes it difficult to achieve high light extraction efficiency.
In contrast, the light reflectance of Ag and Al can be made as high as 90% or more at 450 nm. However, Ag and Al are prone to migration and cause the problem of decreased reliability.